Max... We routinely produce Mil-Std pwb's with characteristic impedence values of up to 100 ohms, relative to the reference plane. I assume that when you refer to the "width of the dielectric", you mean the dielectric separation between the signal layer and its reference plane. We obtain our values with a separation of approx. 10 mils and a trace width of .0065 +/- .0015 mils. However, we are using polyimide which has a better dielectric constant. I may not have totally understood your question, so maybe my answer does't help. However, I can't believe that this is all black magic and you have a very difficult design problem. You may also want to discuss the issues with another supplier. If you would like to discuss this further, please feel free to contact me. Hope it helps. Regards, Bob Vanech Bob Norden Systems (203) 852-4810 *************************************************************************** * The mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To unsubscribe from this list at any time, send a message to: * * [log in to unmask] with <subject: unsubscribe> and no text.* *************************************************************************** * If you are having a problem with the DesignerCouncil, please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * ***************************************************************************